Methods and apparatus for an adjustable stiffness catheter

Abstract

Apparatus and methods for an endovascular catheter that can be inserted within tortuous body anatomies and then selectively stiffened and fixed in place. In a particular embodiment, this stiffness is reversible. The stiffness or a comparable mechanical characteristic of the catheter assembly may be adjusted to a relatively low value during insertion (so that it easily navigates a guide wire or the like), and then subsequently adjusted to a relatively high value in situ to keep the catheter assembly substantially fixed in place (i.e., during delivery of an interventional device).

1 . A catheter apparatus comprising:
 a tubular body having a distal end, a proximal end, and a lumen defined therein; and   activation means for selectably causing the tubular body to enter a first state and a second state;   wherein, in the first state, the tubular body has a first value of a stiffness metric that is below a predetermined navigatibility threshold; and   wherein, in the second state, the tubular body has a second value of the stiffness metric that is above a predetermined rigidity threshold value.   
     
     
         2 . A catheter apparatus comprising:
 a tubular body having a distal end, a proximal end, and a lumen defined therein; and   activation means for selectably causing the tubular body to enter a first state and a second state;   wherein, in the first state, the tubular body has a first value of a stiffness metric;   wherein, in the second state, the tubular body has a second value of the stiffness metric that is greater than the first value; and   wherein the activation means includes a controller communicatively coupled to the tubular body and adapted to place the tubular body in the second state by subjecting at least a portion of the catheter apparatus to a reduction or change in temperature.   
     
     
         3 . A catheter apparatus comprising:
 a tubular body having a distal end, a proximal end, and a lumen defined therein; and   activation means for selectably causing the tubular body to enter a first state and a second state;   wherein, in the first state, the tubular body has a first value of a stiffness metric;   wherein, in the second state, the tubular body has a second value of the stiffness metric that is greater than the first value; and   wherein the activation means includes a controller communicatively coupled to the tubular body and adapted to place the tubular body in the second state by subjecting at least a portion of the tubular body to an increase in axial compression.   
     
     
         4 . The catheter apparatus of  claim 3 , wherein the tubular body comprises a plurality of axial segments responsive to the increase in axial compression. 
     
     
         5 . The catheter apparatus of  claim 4 , wherein the controller includes at least one linkage component mechanically coupled to at least one of the plurality of axial segments and extending to the proximal end of the tubular body. 
     
     
         6 . The catheter apparatus of  claim 5 , wherein the tubular body includes an auxiliary lumen provided therein, and wherein the at least one linkage component includes at least one wire component extending through the auxiliary lumen. 
     
     
         7 . The catheter apparatus of  claim 6 , wherein the tubular body includes at least two auxiliary lumens distributed symmetrically within the tubular body. 
     
     
         8 . The catheter apparatus of  claim 7 , wherein the at least one wire includes two or more wires, and the controller includes a gimble component coupled to the two or more wires, the gimble component configured to apply substantially equal tension on the two or more wires. 
     
     
         9 . The catheter apparatus of  claim 8 , wherein the two or more wires includes four three wires. 
     
     
         10 . A catheter apparatus comprising:
 a tubular body having a distal end, a proximal end, and a lumen defined therein; and   activation means for selectably causing the tubular body to enter a first state and a second state;   wherein, in the first state, the tubular body has a first value of a stiffness metric;   wherein, in the second state, the tubular body has a second value of the stiffness metric that is greater than the first value; and   wherein the activation means includes a controller communicatively coupled to the tubular body and adapted to place the tubular body in the second state by subjecting at least a portion of the tubular body to an increase in radial compression.   
     
     
         11 . The catheter apparatus of  claim 10 , wherein:
 the tubular body includes at least two fluid impermeable layers defining a pressure-responsive chamber;   the tubular body includes at least one interstitial structure provided within the pressure-responsive chamber;   the controller is configured to cause a change in internal pressure within the pressure-responsive chamber; and   the at least one interstitial structure is adapted to exhibit radial compression in response to the change in internal pressure.   
     
     
         12 . The catheter apparatus of  claim 11 , wherein the at least one interstitial structure includes a plurality of laminar members configured to be substantially slideable with respect to each other during the first state, and be substantially non-slideable with respect to each other during the second state. 
     
     
         13 . The catheter apparatus of  claim 12 , wherein the plurality of laminar members comprise a braid or a helically wrapped structure. 
     
     
         14 . The catheter apparatus of  claim 10 ,
 wherein the tubular body includes an outer layer, an inner layer, and one or more interstitial structures provided therebetween; and   wherein the controller includes at least one linkage component mechanically coupled to at least one of the interstitial structures and configured to cause the at least on linkage component to expand and contract radially.   
     
     
         15 . The catheter apparatus of  claim 12 , wherein the at least one interstitial component comprises a substantially cylindrical braided structure. 
     
     
         16 . The catheter apparatus of  claim 12 , wherein the at least one interstial component comprises a helically-wrapped structure. 
     
     
         17 . A catheter apparatus comprising:
 a tubular body having a distal end, a proximal end, and a lumen defined therein; and   activation means for selectably causing the tubular body to enter a first state and a second state;   wherein, in the first state, the tubular body has a first value of a stiffness metric;   wherein, in the second state, the tubular body has a second value of the stiffness metric that is greater than the first value; and   wherein the tubular body includes at least two body segments, the activation means includes a controller rotatably coupled to the at least two body segments, and the controller is configured to apply a relative rotational force between the at least two body segments to cause the tubular body to enter the second state.   
     
     
         18 . The catheter apparatus of  claim 17 , wherein the at least two body segments includes an outer layer, an inner layer, and a torsionally-responsive structure provided therebetween. 
     
     
         19 . The catheter apparatus of  claim 18 , wherein the torsionally-responsive structure comprises a substantially cylindrical braided structure. 
     
     
         20 . A catheter apparatus comprising:
 a tubular body having a distal end, a proximal end, and a lumen defined therein; and   activation means for selectably causing the tubular body to enter a first state and a second state;   wherein, in the first state, the tubular body has a first value of a stiffness metric;   wherein, in the second state, the tubular body has a second value of the stiffness metric that is greater than the first value; and   wherein the tubular body includes at least one inner chamber, a selectably solidifiable material provided within the inner chamber; and a controller fluidly coupled to the at least one inner chamber.   
     
     
         21 . The catheter apparatus of  claim 20 , wherein the solidifiable material is adapted to substantially solidify in response to UV radiation. 
     
     
         22 . The catheter apparatus of  claim 20 , wherein the solidifiable material is adapted to substantially solidify in response to introduction of a catalyst within the inner chamber. 
     
     
         23 . The catheter apparatus of  claim 20 , wherein the solidifiable material is a polymer adapted to substantially solidify in response to a temperature change. 
     
     
         24 . The catheter apparatus of  claim 20 , wherein the solidifiable material includes hydrophilic particles configured to expand when contacting water, and the controller is configured to introduce a volume of water into the inner chamber. 
     
     
         25 . The catheter apparatus of  claim 24 , further including a perfusion lumen provided within the inner chamber, the perfusion lumen fluidly coupled to the controller. 
     
     
         26 . The catheter apparatus of  claim 20 , wherein the solidifiable material is an acoustically-active polymer. 
     
     
         27 . The catheter apparatus of  claim 20 , wherein the solidifiable material is an electroactive polymer (EAP). 
     
     
         28 . A catheter apparatus comprising:
 a tubular body having a distal end, a proximal end, and a lumen defined therein;   activation means for selectably causing the tubular body to enter a first state and a second state; and   a controller adapted to selectably dispense an aqueous mixture;   wherein, in the first state, the tubular body has a first value of a stiffness metric;   wherein, in the second state, the tubular body has a second value of the stiffness metric that is greater than the first value;   wherein the tubular body includes a chamber fluidly coupled to the controller and at least partially bounded by a membrane; and   wherein the membrane is configured to be permeable to a liquid portion of the aqueous mixture and impermeable to a solid portion of the aqueous mixture.   
     
     
         29 . The catheter apparatus of  claim 28 , wherein the aqueous mixture is a saline mixture. 
     
     
         30 . A catheter apparatus comprising:
 a tubular body having a distal end, a proximal end, and a lumen defined therein;   activation means for selectably causing the tubular body to enter a first state and a second state; and   a controller comprising a voltage source;   wherein, in the first state, the tubular body has a first value of a stiffness metric;   wherein, in the second state, the tubular body has a second value of the stiffness metric that is greater than the first value; and   wherein the activation means includes at least one shape-memory metallic structure provided within the tubular body and communicatively coupled to the voltage source.   
     
     
         31 . The catheter apparatus of  claim 30 , wherein the shape-memory metallic structure comprises a Ni/Ti alloy. 
     
     
         32 . The catheter apparatus of  claim 30 , wherein the stiffness metric is a measurement of the bending stiffness of the tubular body. 
     
     
         33 . The catheter apparatus of  claim 30 , wherein the stiffness metric is a catheter pull-out metric. 
     
     
         34 . The catheter apparatus of  claim 30 , wherein the tubular body has a plurality of zones, each zone having a corresponding stiffness metric while in the second state. 
     
     
         35 . The catheter apparatus of  claim 34 , wherein, within a first zone, the stiffness metric of the tubular body varies continuously along its length while in the second state. 
     
     
         36 . The catheter apparatus of  claim 35 , wherein a first zone is adjacent the distal end of the tubular body, and a second zone is adjacent the first zone, further wherein the corresponding stiffness metric of the first zone is less than the corresponding stiffness metric of the second zone while in the second state. 
     
     
         37 . The catheter apparatus of  claim 30 , wherein, while in the second state, the tubular body has the second stiffness value along a first curvature axis and a third stiffness value along a second curvature axis that is orthogonal to the first curvature axis. 
     
     
         38 . The catheter apparatus of  claim 30 , wherein the activation means is coupled to a controller provided at the proximal end of the tubular body. 
     
     
         39 . The catheter apparatus of  claim 30 , wherein the activation means is communicatively coupled to a controller configured to be slideably inserted within the lumen. 
     
     
         40 . The catheter apparatus of  claim 30 , wherein the activation means is coupled to a controller that is remote from the tubular body. 
     
     
         41 . The catheter apparatus of  claim 30 , wherein the tubular body includes a helical channel formed therein. 
     
     
         42 . The catheter apparatus of  claim 30 , wherein the tubular body includes a plurality of ring-shaped channels formed circumferentially therein. 
     
     
         43 . The catheter apparatus of  claim 42 , wherein the plurality of ring-shaped channels are distributed irregularly along the tubular body.